The spoof horror writer Garth Marenghi scooped the Perrier comedy award in Edinburgh yesterday after a contest soured by protests over powdered milk and accusations that the event had lost its sparkle.

Marenghi, whose merciless lampooning of pulpy horror novels has won widespread critical acclaim, fought off competition from four other male contenders for the £5,000 award, which has traditionally been seen as one of the high points of the Edinburgh festival fringe.

This year, however, the award scheme was attacked by former winners Rob Newman and Emma Thompson, who backed calls for a boycott by the group Baby Milk Action because of the involvement of Perrier's owners, Nestlé, in marketing powdered baby milk in developing countries.

Yesterday, Nica Burns, director and producer of the awards, rebutted the criticism and accused those who had called for a boycott of "breaking the spirit of the fringe".

Other critics, however, said the awards, which were celebrating their 21st anniversary this year, had lost their edge and had been devalued by the lack of female nominees. For the sixth year running there were no female comics on the final shortlist. Jenny Eclair was the last woman to win the prize, in 1995.

The award is still considered one of the biggest accolades in comedy, however, and previous winners, including Steve Coogan, Frank Skinner and the League of Gentlemen, have used it as a springboard for their showbiz careers.

The Garth Marenghi team will now have the opportunity to appear in London as part of the acclaimed Perrier Pick of the Fringe Season in the West End in October.

This year's show centred around Marenghi's latest work, Netherhead, said to be the darkest book he has ever written. "It will peel back the layers of your mind until your brains fall out." Marenghi's previous works include Dawn Waters, a terrifying tale of urine infection; Black Fang (Rats learn to drive); and Slicer, a novel about a flying knife.

Speaking yesterday, Marenghi - who won't reveal his off-stage alter ego - said he was delighted to receive the award and had been inspired in his latest work by a bout of sickness and an eye infection. "Bram Stoker ate a bad crab; Robert Louis Stevenson had a gippy tummy - well, he was quite ill, actually; and I had flu and a stye."

Asked for his reaction to the baby milk protests, Marenghi's publisher, Dean Learner, said: "I have instructed Garth not to discuss anything he doesn't understand."

The other nominees for the 2001 award were Dan Antopolski for his show Antopolski 2000, Jason Byrne, Australian-born Adam Hills (Go You Big Red Fire Engine), and Daniel Kitson (Love, Innocence and the Word Cock).

Meanwhile, it emerged yesterday that Edinburgh city council is considering introducing an X-rating for some fringe shows next year to ensure children are not exposed to unsuitable material.

City officials said it is was not always clear from promotional literature what kind of material the shows actually contained and parents needed more information.

"It is embarrassing for the comedian, for the rest of the audience and I'm sure for the parents when young children are in the audience," said Steve Cardownie, the council's arts convener.

"I will be looking at doing anything the council can within its powers to give parents as much guidance as possible."